1. Field of the Invention
The invention relates to a cadmium electrode for alkaline batteries and to a method of manufacturing the aforementioned electrodes.
2. Discussion of the Background Information
Cadmium electrodes for batteries are at present made by two main methods. In the first method, a sintered nickel substrate is impregnated with cadmium hydroxide Cd(OH).sub.2 by chemical means (precipitation). In the second and more recent method, a mixture of cadmium oxide CdO+binder is deposited on a metal substrate, which is usually a reeled- out piece or strip of perforated nickel-plated steel.
In recent years, cellular metal structures, e.g. of foamed nickel, have become commercially available, and have accordingly been used as collectors, into which the mixture of CdO+binder is introduced. It might be expected that these structures would facilitate drainage of charges into the active material, thus increasing the capacitive efficiency of the CdO material constituting the electrode.
In this connection, it has been known for more than five years that addition of nickel to the mixture of CdO+binder has an advantageous effect on efficiency.
In most of the articles, mostly Soviet, published on this subject, nickel is introduced in the form of metal powder or nickel hydroxide. The possibility of introducing nickel in the form of sulphate or nitrate is mentioned in only one publication, by V. M. Negeevich, G L. Marchenko, L. N. Sagoyan and V. D. Kushkov in Vopr. Khim. Khim. Technol. 87, (1988), 6-11. With a view to obtaining maximum efficiency, these authors have defined an Ni(OH).sub.2 /CdO ratio of 0.08. In their tests, the ratios were between 0.01 and 0.15.
As far as the applicants know, however, the aforementioned authors did not work with foamed nickel substrates.